VENTILATION STRATEGY FOR SUBWAY CABINS USING NUMERICAL SIMULATIONS

초록

More than 7 million passengers use the Seoul Metropolitan Subway (SMS) everyday and this number has been increasing. With the increasing trends in concerns over indoor air quality (IAQ), the management of IAQ has become an important issue, especially in the case of subway operators, because most of subway lines are placed underground with poor ventilation conditions. The SMS is known to be the one of the most heavily used transportation means in the world. The subway cabins are naturally ventilated when the cabin doors are opened and through the gaps caused by the incomplete air-tightening of cabin bodies. Although, subway trains are equipped with a mechanical exhaust fan, the apparatus is rarely operated due to the problem of heating/cooling efficiency especially in the summer and winter seasons. In this study, we analyzed the transient carbon ioxide (CO2) concentration level during the journey of a subway cabin when a heavy load of passengers of up to 200% of designed capacity using a computational fluid dynamics (CFD) analysis. Air streamlines were analyzed and CO2 output by passenger was related with flow patterns during the cooling of the cabin. With an increased journey time, the CO2 concentration increased by up to 5,000 ppm depending on passenger load. Through the operation of a mechanical exhaust fan, the high concentration of CO2 decreased down to 1,500 ppm.